Drive means for motor vehicles

ABSTRACT

Drive means for motor vehicles, comprising an internal combustion engine ( 1 ) and an unsynchronised autoshift gearbox ( 9 ). The clutch and the gearbox are s controlled by an electronic transmission control unit ( 45 ) which communicates with an engine control unit ( 48 ), to which are fed signals representing the selected gear from a gear selector ( 46 ) and signals representing various engine and vehicle data. The input shaft of the gearbox is coordinated with a torque sensor ( 60 ), which provides a signal dependent of the torque on the input shaft to to the transmission control unit, which is disposed to continuously register the current torque on the input shaft and utilize the torque signal from the torque sensor to calculate the current vehicle motion resistance. The gear selection is made here based on the calculated vehicle motion resistance.

The present invention relates to a drive means for motor vehicles,comprising an internal combustion engine and an automated shift gearbox,which has an input shaft drivingly joined to the engine crankshaft andwhich is controlled by a control means, connected to a gear selector,and having a transmission control function and an engine controlfunction, and to which are fed signals representing the selected gearand various engine and vehicle data, which comprise at least enginespeed, rotational speed of the transmission input shaft and vehiclespeed.

In today's automated shifting systems, information on vehicle motionresistance, including rolling resistance, air resistance and roadincline, to select the gear in the best manner. It is thereforeimportant that the estimation of vehicle motion resistance be as exactas possible. One method of estimating vehicle motion resistance is tocompare the engine torque, which is the torque corresponding to thecurrent injected amount of fuel, with vehicle acceleration and mass (theresisting force=the driving force to the drive wheels−vehiclemass×vehicle acceleration). This method involves however a number ofuncertain factors. If, for example, an auxiliary unit, such as a coolingfan, an air compressor or an AC compressor, is engaged it will mean thatthe torque signal cannot be used directly for estimating the vehiclemotion resistance without compensating for the torque to the auxiliaryunits. If one or more auxiliary units are engaged, the current injectedamount of fuel will indicate a greater vehicle motion resistance thatwhat is actually the case. Furthermore fuel quality, engine wear andvariations between individual engines will also affect the result.

The purpose of the present invention is to achieve a drive unit formotor vehicles of the type described by way of introduction, whichprovides a more reliable estimate of the actual vehicle motionresistance to thereby make possible improved gear selection.

This is achieved according to the invention by virtue of the fact thatthat the input shaft of the gearbox is coordinated with a torque sensor,which provides a signal dependent on the torque on said input shaft tosaid control means, and that the control means are arranged tocontinuously register the current torque on the input shaft, to utilizethe torque signal from the torque sensor for calculating the currentvehicle motion resistance and selecting a gear on the basis of thecalculated vehicle motion resistance.

Through the invention, the actual resistance to vehicle motion isutilized when selecting a gear, eliminating the effect of any engagedauxililiary units, fuel quality or engine wear.

The invention will be described in more detail with reference toexamples shown in the accompanying drawings, where FIG. 1 shows aschematic representation of a drive unit according to the invention andFIG. 2 shows the clutch and the gearbox of FIG. 1 on a larger scale.

In FIG. 1, 1 designates a six-cylinder internal combustion engine, e.g.a diesel engine, the crankshaft 2 of which is coupled to a single-discdry-disc clutch, gene-rally designated 3, which is enclosed in a clutchbell 4. Instead of a single disc clutch, a dual disc clutch canbe used.The crankshaft 2 is solidly joined to the clutch housing 5, while itsdisc 6 is solidly joined to an input shaft 7 (FIG. 2) which is rotatablymounted in the housing 8 of a gearbox, generally designated 9. A mainshaft 10 (FIG. 2) and an intermediate shaft 11 (FIG. 2) are rotatablymounted in the housing 8.

As is most clearly evident from FIG. 2, a gear 12 is rotatably mountedon the input shaft 7 and can be locked to such shaft with the aid of anengaging sleeve 13 provided with synchronizing means. Said engagingsleeve 13 is non-rotatably but axially displaceably mounted on a hub 14non-rotatably connected to the input shaft. With the aid of the engagingsleeve 13, a gear 15, rotatably mounted on the main shaft 10, islockable relative to the input shaft 7. The gears 12 and 15,respectively, engage gears 16 and 17, respectively, which arenon-rotatably joined to the intermediate shaft 11. Additional gears 18,19 and 20, respectively, are non-rotatably joined to the intermediateshaft 11 and engage gears 21, 22 and 23, respectively, on the main shaft10 and lockable to the main shaft with the aid of engaging sleeves 24and 25, respectively, which in the example shown do not havesynchronizing means. On the main shaft 10, an additional gear 28 isrotatably mounted and engages an intermediate gear 30 rotatably mountedon a separate shaft 29. The intermediate gear 30 engages in turn anintermediate shaft gear 20. The gear 28 is lockable to its shaft withthe aid of an engaging sleeve 26.

The gear pairs 12, 16 and 15, 17 and the engaging sleeve 13 form asplitter group with a low stage LS and a high stage HS. The gear pair15, 17 together with the gear pairs 21, 18, 22, 19,23,20 and 28, 30 forma main group with four speeds forward and one reverse. At the output endof the main shaft 10, a gear 31 is non-rotatably mounted to form the sungear in a two-range group of planetary type, generally designated 32,the planet carrier 33 of which is non-rotatably mounted to a shaft 34,forming the output shaft of the gearbox. The planet gears 35 of therange group 32 engage a ring gear 36 which, with the aid of an engagingsleeve 37, can be locked relative to the gearbox housing 8 for low rangeLR and relative to the planet carrier 33 for high range HR The engagingsleeve 37 also has a neutral position NR lying between low range LR andhigh range HR, in which neutral position the output shaft 34 is releasedfrom the main shaft 10.

The engaging sleeves 13, 24, 25, 26 and 37 are displaceable as indicatedby the arrows in FIG. 2, providing the gear positions indicated abovethe arrows. Displacement is achieved by servo means 40, 41, 42, 43 and44, schematically indicated in FIG. 2, which can be pneumaticallyoperated piston-cylinder devices of the type used in a gearbox of theabove described type, which is marketed under the name Geartronic®. Theservo means are controlled by an electronic control unit 45 (FIG. 1),comprising a microcomputer depending on signals fed into the controlunit representing various engine and vehicle data, including at leastengine speed, vehicle speed, clutch and accelerator pedal position and,where applicable, engine brake on-off, when an electronic gear selector46 coupled to the control unit 45 is in its automatic position. When theselector is in its position for manual shifting, the shifting occurs atthe command of the driver via the gear selector 46. The control unit 45also controls the fuel injection, i.e. the engine speed, depending onthe accelerator pedal position and the air supply to a pneumaticpiston-cylinder device 47, by means of which the clutch 3 is engaged anddisengaged.

The transmission control unit 45 is programmed in a known manner so thatthe clutch 3 is held engaged when the vehicle is standing still and thegear selector 46 is in the neutral position. This means that the engineis driving the input shaft 7 and thus also the intermediate shaft 11,while the output shaft 34 is disengaged. Supplementary apparatus drivenby the intermediate shaft, e.g. an oil pump for lubricating the gearbox,is driven in this position. The control unit 45 is also programmed, whenthe vehicle is standing still and the gear selector is moved from theneutral position to a gear engaging position, either to a position forautomated shifting or to a position with a driver selected starting offgear, to first release the clutch 3 and then brake the intermediateshaft 11 to stop with the aid of the intermediate shaft brake 50indicated in FIG. 2, and which can be a braking device of a type knownper se and controlled by the control unit 45. With the intermediateshaft 11 braked to stop or at least nearly to stop, the control unit 45now initiates shifting in the main group a starting off gear whichprovides the total gear ratio selected by the automated transmission orby the driver. When the driver, after engagement of the selectedstarting-off gear, e.g. first gear, depresses the accelerator, theaccelerator pedal will function as a reversed clutch pedal, which, viathe transmission control unit successively increases the clutchengagement with increasing throttle opening.

When shifting—initiated either directly by the driver or by automaticcontrol means in accordance with a gear selection strategy stored in thetransmission control unit 45, which can take into account hw the vehiclesurroundings will appear in the immediate future, the transmissioncontrol unit 45 first controls the engine control unit 48 to regulatethe fuel supply to the engine, so that a torqueless or practicallytorqueless state is created in the vehicle drive chain. In other words,the torque transmission from the engine crankshaft 2 to the input shaft7 of the gearbox 9 must be zero or at least practically zero. Thetransmission control unit 45 receives continuous information on, andregisters the current engine torque via, the amount of fuel injected.

The transmission unit 45 also receives continuous information on currenttorque on the gearbox input shaft 7 via a torque sensor 60 coupled tothe input shaft. The sensor can be of a type known per se and used inlaboratory contexts The sensor utilizes the signal from the torquesensor 60 to compute the current vehicle resistance. The transmissioncontrol unit 45 thus determines the gear and the moment of engagementbased on the actual resistance to vehicle motion and not on the basis ofthe engine load, which is affected by the load from one or more engagedauxiliary units. 61 designates generally one or more auxiliary units,which are driven from one or more engine driven/engine mounted powertake-offs 62 before the clutch 3. The auxiliary units 61, for example ahydraulic pump, a cooling fan, a generator, an air compressor or an ACcompressor, can be engaged to be driven by the engine or can bedisengaged by manual and/or automatic controls 63 coupled to the enginecontrol unit 48.

The invention has been described above with reference to a steppedunsynchronised autoshift gearbox, but the principle of using a torquesensor on the input shaft of an automated shift transmission and usingthe torque signal from the torque sensor to calculate the vehicle motionresistance and select the gear, is of course not limited to this type ofautomatic transmission, but can be used on other types of automatedtransmissions, such as those using torque converters and planet gearingsteps.

1. Drive unit for motor vehicles, comprising an internal combustionengine (1) and an automated shift gearbox, which has an input shaftdrivingly joined to the engine crankshaft and which is controlled by acontrol means (45, 48), connected to a gear selector (46), and having atransmission control function and an engine control function, and towhich are fed signals representing the selected gear and various engineand vehicle data, which comprise at least engine speed, rotational speedof the transmission input shaft and vehicle speed, characterized in thatthe input shaft (7) of the gearbox is coordinated with a torque sensor(60), which provides a signal dependent on the torque on said inputshaft to said control meanss, and that the control means (45,48) arearranged to continuously register the current torque on the input shaft,to utilize the torque signal from the torque sensor for calculating thecurrent vehicle motion resistance and selecting a gear on the basis ofthe calculated vehicle motion resistance.
 2. Drive means according toclaim 1, characterized in that the gearbox is a step gearbox and has aninput shaft (7) connected via a disc clutch (3) to the enginecrankshaft, said step gearbox (9) having at least one intermediate shaft(1 ). mounted in a housing, said intermediate shaft (11) having at leastone gear (16, 17) in engagement with a gear (12, 15) on the input shaft,a main shaft (10) which is mounted in the housing and has gears (15, 21,22, 23) engaging gears (17, 18, 19, 20) on the intermediate shaft, atleast one gear in each pair of interengaging gears on the intermediateshaft and the main shaft being rotatably mounted on its shaft andlockable by engaging means (13, 24, 25) of which at least some forwardgears lack a synchronization function.